BEIJING —
At least 31 people have been killed in an attack on a street market in the capital of China's restive region Xinjiang. Chinese state media say two cars plowed into a market street, running people over and throwing explosives against the crowd.

The attack occurred Thursday morning as many were buying vegetables and fruit at a roadside market in a largely Chinese neighborhood in the regional capital, Urumqi. At least 90 people were also wounded.

Pictures posted online from witnesses showed chaotic scenes with bodies in the street and flames from the explosions.

Chinese media said the attackers drove two cars, which crashed through a metal barricade and plowed into crowds of morning shoppers.

A local resident who lives in a compound facing the market says she was woken from her sleep by loud sounds. When she went outside, she said many people were paralyzed with fear. Witnesses told her two cars drove back and forth down the lane tossing bombs as they did.

Authorities have yet to provide any details about what happened to the assailants, but called the attack an act of terrorism. The bombings are the third major incident in China in recent months. Late last month, a bomb attack at Urumqi's train station left three people dead and 79 injured.

The following is a timeline of recent violence blamed by Beijing on Xinjiang separatists or foreign-backed militants:

- October 28: Three attackers ram a car into a group of people in Tiananmen Square; two tourists killed, 38 injured

- March 1: Passengers at a train station in Yunnan province attacked by eight knife-wielding men; 29 killed, over 140 injured.

- April 30: Two attackers set off explosives, slash passengers at Urumqi train station; one killed, 79 injured.

- May 22: Two cars plow through busy market in Urumqi, set off explosives; 31 dead, over 90 injured.

Despite a nationwide crackdown on terrorism and beefed up security at train stations in Xinjiang and across the country, the attacks continue.

Foreign Ministry spokesman Hong Lei.

Hong Lei says the "Chinese government has the confidence and ability to combat terrorists." Hong says the terrorists are "swollen with arrogance and their schemes will not succeed."

The western region of Xinjiang is home to many Uighur people, a largely Muslim minority ethnic group in China. The government has blamed at least two recent attacks, the one last month in Urumqi and a bloody knife attack in early March, on extremist Uighur terrorists.

Xinjiang has long been the site of ethnic unrest and tensions between China's Han majority and its ethnic Uighur minorities.

Uighurs frequently complain about the government's oppressive religious and cultural policies in the region. As Beijing has tightened its grip over the past year, carrying out what it says is a crackdown on terrorism, there has been an uptick in the number incidents of violence, which appears to be spreading beyond Xinjiang.

The government says terrorists were behind an attack on Tiananmen Square late last year, and at train stations in Kunming and Urumqi more recently.

China has blamed the train station attacks on a group called the Turkestan Islamic Party. The group has posted videos online praising the train station assault, and called on people in Xinjiang to take part in the holy war, or jihad, against the Chinese government.

Rohan Gunaratna, who studies terrorism at Singapore's Nanyang Technological University believes TIP could be behind Thursday's attack as well.

"There is no group that has the operational skill and the will to mount an attack of this scale in Xinjiang than the Turkestan Islamic Party," said Gunaratna.

In response to the violence, Chinese authorities have been beefing up security in Xinjiang as well as in train stations and other transportation hubs of cities around China.

Gunaratna says that physical and operational security will not be sufficient alone. China, he says, needs to strengthen its intelligence capabilities.

"China needs to recruit more sources (in Xinjiang) and infiltrate the Turkestan Islamic Party, without that it will be difficult to develop high-quality, high-grade intelligence," said Gunaratna.

Gunarata adds that as the U.S. draws down in Afghanistan, the terrorist threat to China is likely to grow. The Chinese Foreign Ministry has said that terrorist cells trained in Pakistan have organized acts of violence in Xinjiang with the intent of splitting the country.